The present invention relates to stencil printing machines for transferring print medium in pressured state between a printing drum, to which a stencil sheet is mounted, and a press rotary member to press the printing drum to perform a printing operation and, more particularly, to a stencil printing machine having two sets of printing drums and press rotary members for performing a double-face printing operation.
FIG. 1 shows a schematic overall structure of a conventional a stencil printing machine that enables a double-face printing operation. As shown in FIG. 1, the stencil printing machine 100 is constructed of upstream and downstream stencil making sections 104, 105 with respective thermal printing heads 102, 103 for thermally perforating respective stencil sheets 101, 101 on the basis of respective image data, an upstream printing section 109 wherein the stencil sheet 101 made in the upstream stencil making section 104 is mounted onto an upstream printing drum 106 and a print sheet 107, which is fed thereto, is transferred through a path between the upstream printing drum 106 and a press roller 108 in a pressured contact relationship to transfer ink onto an upper surface (one surface) of the print sheet 107 during such a transfer step, a paper feed section 110 which feeds the print sheet 107 to the upstream printing section 109, an upstream belt-conveyer transfer unit 111 located at a sheet discharge side of the upstream printing section and transferring the print sheet 107 to a downstream side with the action of a belt 121, a downstream printing section wherein the stencil sheet 101, which is made in the downstream stencil making section 105, is mounted onto a downstream printing drum 112 and the print sheet, which is fed from the upstream belt conveyer transfer unit 111, is transferred through a path between the printing drum 112 and a press roller 114 in a pressured contact relationship to transfer ink onto a lower surface (the other surface) of the print sheet 107 during such a transfer step, and a downstream belt-conveyer transfer unit 117 with a belt 122 located at a sheet discharge side of the downstream printing section 115 for transferring the print sheet 107 to a sheet discharge tray 116 located in a downstream side.
Further, the upstream and downstream printing sections 109, 115 include squeegee rollers 123, 123 located inside the printing drums 106, 112, respectively, and held in contact with inner surfaces of outer peripheral walls 106a, 112a of the respective printing drums 106, 112, doctor rollers 124, 124 located in close proximity to the squeegee rollers 123, 123, respectively, to form respective given gaps relative thereto, and ink supply units 125, 125 each for supplying ink to an each area between the rollers 123, 124, with the squeegee rollers 123, 123 being arranged to rotate on inner peripheral surfaces of the outer peripheral walls 106a, 112a in association with rotations of the respective printing drums 106, 112. In addition, as the squeegee rollers 123, 123 rotate with the rotations of the printing drums 106, 112, the outer peripheral surfaces of the squeegee rollers 123, 123 are adhered with ink in a given film thickness, with the adhered ink being transferred to the outer peripheral walls 106a, 112a to allow ink to be supplied to an inner side of the stencil sheet 101 at all times.
Now, the double-face printing operation is described below. Rotations of the printing drums 106, 112 allow the print sheet 107 to be fed from the paper feed section 110 to the upstream printing drum 106 in synchronism with the rotation thereof. The print sheet 107, thus fed to the printing drum 106, is brought into pressured contact with the stencil sheet 101 of the printing drum 106 with the press roller 108 to allow ink image to be transferred onto the upper surface of the print sheet 107, with the print sheet 107, whose upper surface is printed, being peeled off from the outer peripheral wall of the printing drum 106 and being introduced to the upstream conveyer-belt transfer unit 111. The upstream belt-conveyer transfer unit 111 causes the belt 121 to move for transferring the print sheet 107 with its lower surface remaining contact with the belt, thereby feeding the print sheet 107 from the most downstream side of the belt 121 to the downstream printing drum 112. The print sheet 107, thus fed to the downstream printing drum 106, is then brought into pressured contact with the stencil sheet 101 of the printing drum 112 with the press roller 114 to transfer ink image onto the lower surface of the print sheet 107, with the print sheet 107, whose lower surface is printed, being peeled off from the outer peripheral wall of the printing drum 112 to be introduced to the downstream belt-conveyer transfer unit 117. The downstream belt-conveyer transfer unit 117 causes the belt 122 to move for transferring the print sheet 107 from the most downstream side of the belt 122 to the sheet discharge tray 116. The print sheet 107 thus discharged to the sheet discharge tray 116 is placed therein in the stacked state.
Also, a similar technology related to such a stencil printing machine 100 is disclosed in Japanese Patent Provisional Publication No. 8-90893.
By the way, in the aforementioned stencil printing machine for the double-phase printing operation, the print sheet 107, whose upper surface has been printed with the upstream printing section 109, is fed to the downstream printing section 115 in a non-fixed ink state to cause the press roller 114 of the downstream printing section 115 to press the upper surface, which remains in the non-fixed ink state, of the print sheet 107. Accordingly, as shown in FIG. 2, the outer circumferential periphery of the press roller 114 and non-fixed ink 130 of the print sheet 107 are brought into surface contact in a wide range. For this reason, when the press roller 114 is separated from the print sheet 107, non-fixed ink area 130 remaining at the contact surface is caused to be split such that a portion of non-fixed ink 130 is adhered to the press roller 114. When this takes place, non-fixed ink is transferred to the press roller 114 and is then transferred to the print sheet 107, providing an issue of contamination in the print sheet 107.
To address such an issue, it is thought for providing a means for washing ink transferred to the press roller 114 with a waste.
However, with such a means for washing ink adhered to the press roller 114, a mechanism for washing becomes complicated in structure and, also, a new issues is encountered in that ink is transferred from the print sheet 107 to the press roller 114, resulting in a decrease in the print density of the print sheet 107.
On the other hand, with such a stencil printing machine which enables only a single-phase printing operation, when the print sheet is not fed between the printing drum and the press roller to cause the press roller to be brought into direct contact with the stencil sheet owing to a jamming operation, when the print sheet whose size is smaller than a lateral size of the stencil sheet and a portion of the press roller is brought into direct contact with the stencil sheet and when the single-phase printing operation is implemented and the other surface of the print sheet in non-fixed ink state is subjected to the printing operation, there are some instances wherein ink is transferred to the press roller and transferred ink is further transferred to the print sheet, with a resultant contamination in the print sheet.
The present invention has been made to address the aforementioned issue and has an object to provide a stencil printing machine which is able to prevent print medium from being contaminated with little decrease in a print density of print medium with a simplified structure.
An important feature of the invention concerns a stencil printing machine having a printing section composed of a rotary printing drum with an outer circumferential periphery to which a stencil sheet is mounted and a rotary press member which is moveable between a pressurized position to be pressed against the outer circumferential periphery of said printing drum and a separated position to be separated from the outer circumferential periphery of said printing drum, and a paper feed section for feeding print medium between said printing drum and said rotary press member, wherein print medium, fed from the paper feed section, is pressed between and transferred by said printing drum and said rotary press member both of which are rotated together, and during such a pressurized and transfer movement of print medium, print medium is transferred with ink to perform a printing operation, and wherein the stencil printing machine comprises said rotary press member including an outer circumferential periphery formed with micro-convexities and micro-concavities.
With such a stencil printing machine, contamination of print medium is prevented only by providing the micro-convexities and the micro-concavities over the outer circumferential periphery of the rotary press member so that even when the rotary press member is brought into directly pressured contact with the stencil sheet, the rotary press member has a decreased contact surface area with ink, or the outer circumferential periphery of the rotary press member has a reduced contact surface area with the surface, with non-fixed ink, of print medium and, when the rotary press member is separated from the stencil sheet, or when the rotary press member is separated from print sheet, aforementioned ink or non-fixed ink, which remains at a portion with which the rotary press member is not brought into contact, are not adhered to the rotary press member to interrupt the rotary press member from being appreciably adhered with non-fixed ink.
Another important feature of the invention concerns the stencil printing machine wherein said micro-convexities and said micro-concavities of the outer circumferential periphery of said rotary press member has a depth of a value above 0.035 mm.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, when the rotary press member presses the printing drum via print medium, there is a big difference in level in the convexities and the concavities to interrupt the concavities from being practically brought into contact with non-fixed ink of print medium, thereby adequately minimizing transfer of non-fixed ink to the rotary press member.
Another important feature of the invention concerns the stencil printing machine wherein said micro-convexities and said micro-concavities of the outer circumferential periphery of said rotary press member has a depth of a value above 0.044 mm.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, when the rotary press member presses the printing drum via print medium, there is an adequately big difference in level in the convexities and the concavities such that the concavities have little or no contact with non-fixed ink of print medium, thereby further minimizing transfer of non-fixed ink to the rotary press member.
Another important feature of the invention concerns the stencil printing machine wherein a distance between apexes of said micro-convexities and said micro-concavities of the outer circumferential periphery of said rotary press member has a value below 0.64 mm.
With such a stencil printing machine, the effects of the invention is obtained and, in addition, when the rotary press member presses the printing drum via print medium, there is a narrow distance between the convexities and the concavities formed over the outer circumferential periphery of the rotary press member, interrupting the print image from appearing a visible convexity and concavity pattern.
Another important feature of the invention concerns the stencil printing machine wherein said micro-convexities and said micro-concavities of the outer circumferential periphery of said rotary press member are composed of point-like convexities and concavities.
With such a stencil printing machine, the effects of the invention are obtained and, in addition, the convexities and the concavities can be uniformly formed in either direction over the outer circumferential periphery of the rotary press member.
Another important feature of the invention concerns the stencil printing machine wherein said micro-convexities and said micro-concavities of the outer circumferential periphery of said rotary press member are composed of line-shaped convexities and concavities which are orientated in the same direction as that which print medium is transferred.
With such a stencil printing machine, the effects of the invention are obtained and, in addition, the convexities and the concavities can be regularly and distinctly formed over the outer circumferential periphery of the rotary press member in a direction perpendicular an axial direction thereof.
Another important feature of the invention concerns the stencil printing machine wherein said micro-convexities and said micro-concavities of the outer circumferential periphery of said rotary press member are formed by locating a screen mesh to a surface of said rotary press member.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, the screen mesh per se is individually prepared whereupon the screen mesh is located over the outer circumferential periphery of the rotary press member by covering or by adhering for thereby enabling formation of the micro-convexities and the micro-concavities.
Another important feature of the invention concerns the stencil printing machine wherein said point-like micro-convexities and micro-concavities of the outer circumferential periphery of said rotary press member are formed by locating a large number of spherical bodies to a surface of said rotary press member.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, the large number of spherical bodies per se are individually prepared whereupon the spherical bodies are located over the outer circumferential periphery of the rotary press member by adhesion for thereby enabling formation of the micro-convexities and the micro-concavities.
Another important feature of the invention concerns the stencil printing machine, which further comprises a liquid application unit for applying liquid to the outer circumferential periphery of said rotary press member.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, during separating movement between the rotary press member and print medium, a non-fixed ink area is not split whereas a liquid area is split, thereby preventing non-fixed ink from being adhered to the rotary press member.
Another important feature of the invention concerns the stencil printing machine, wherein said liquid has a viscosity of a value below 1000 millipascalxc2x7second (mPaxc2x7s).
With such a stencil printing machine, the effect of the invention is obtained and, in addition, during separating movement between the rotary press member and print medium, the liquid area, which has the low viscosity, is reliably split, thereby preventing non-fixed ink from being adhered to the rotary press member.
Another important feature of the invention concerns the stencil printing machine, wherein said liquid has a viscosity of a value below 500 millipascalxc2x7second (mPaxc2x7s).
With such a stencil printing machine, the effect of the invention is obtained and, in addition, during separating movement between the rotary press member and print medium, the liquid area, which has the lower viscosity, is more reliably split, thereby preventing non-fixed ink from being adhered to the rotary press member.
Another important feature of the invention concerns the stencil printing machine, wherein said liquid is composed of silicone oil.
With such a stencil printing machine, the effects of the invention are obtained with the use of silicone oil.
Another important feature of the invention concerns the stencil printing machine, wherein said liquid application unit comprises a rotary liquid application roller held in pressured contact with said rotary press member, and a liquid supply unit for supplying liquid to an outer circumferential periphery of said liquid application roller, wherein said liquid application roller is rotatable with said rotary press member to apply liquid, supplied by said liquid supply unit, to the outer circumferential periphery of said rotary press member.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, the liquid application roller rotates with the rotary press member to apply liquid to the rotary press member.
Another important feature of the invention concerns the stencil printing machine, wherein said liquid application unit comprises a sheet-like member held in abutting contact with said rotary press member and impregnated with liquid, said sheet-like member being moveable while held in abutting contact with said rotary press member.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, the sheet-like member, impregnated with liquid, enables to be brought into abutting contact with the rotary press member at variable positions.
Another important feature of the invention concerns the stencil printing machine, wherein said liquid application unit comprises a biasing member held in abutting contact with said rotary press member and impregnated with liquid which is retained in said biasing member, and a liquid supply unit for supplying liquid to the outer circumferential periphery of said rotary press member at a point upstream of said biasing member in a direction which said rotary press member rotates.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, liquid is first supplied to the rotary press member with the liquid supply unit and is then smoothly applied over the outer circumferential periphery of the rotary press member with the biasing member, enabling adjustment of the amount of liquid to be applied to the rotary press member with the liquid supply unit.
Another important feature of the invention concerns the stencil printing machine, wherein said liquid application unit comprises a sheet-like member held in abutting contact with said rotational press member at an adjustable contact area and moveable to vary the position of said adjustable contact area, and a liquid supply unit for supplying liquid to the outer circumferential periphery of said rotary press member at a point upstream of said adjustable contact area of said sheet-like member in a direction which said rotary press member rotates.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, liquid is first supplied to the rotary press member with the liquid supply unit and is then smoothly applied over the outer circumferential periphery of the rotary press member with the sheet-like member which can be brought into abutting contact with the rotary press member at variable positions, thereby enabling adjustment of the amount of liquid to be applied to the rotary press member with the liquid supply unit.
Another important feature of the invention concerns the stencil printing machine which has two sets of printing sections located at an upstream side and a downstream side, respectively, and each composed of a rotary printing drum with an outer circumferential periphery to which a stencil sheet is mounted and a rotary press member which is movable between a pressurized position to be pressed against the outer circumferential periphery of the printing drum and a separated position to be separate from the outer circumferential periphery, a paper feed section for feeding print medium to the printing section at the upstream side, and an upstream transfer mechanism for transferring and feeding print medium, discharged from the printing section at the upstream side, to the printing section at the downstream side, wherein print medium, fed from the paper feed section to the printing section at the upstream side, is pressed between and transferred by the printing drum at the upstream side and the rotary press member both of which are rotated together, and during such a pressurized and transfer movement of print medium, one surface of print medium is transferred with ink and print medium is then fed to the printing section at the downstream side with the upstream transfer mechanism to allow print medium to be pressurized between and transferred by the printing drum and the rotary press member at the downstream side such that during such a pressurized and transfer movement, the other surface of print medium is transferred with ink to perform a double-phase printing operation, and which comprises at least said rotary press member, located at the downstream side, including an outer circumferential periphery formed with micro-convexities and micro-concavities.
With such a stencil printing machine, the effect of the invention defined in claim 17 is obtained and, in addition, when the rotary press member presses the printing drum via print medium, there is a big difference in level in the convexities and the concavities to interrupt the concavities from being practically brought into contact with non-fixed ink of print medium, thereby adequately minimizing transfer of non-fixed ink to the rotary press member.
Another important feature of the invention concerns the stencil printing machine wherein said micro-convexities and said micro-concavities of the outer circumferential periphery of said rotary press member has a depth of a value above 0.035 mm.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, when the rotary press member presses the printing drum via print medium, there is a big difference in level in the convexities and the concavities to interrupt the concavities from being practically brought into contact with non-fixed ink of print medium, thereby adequately minimizing transfer of non-fixed ink to the rotary press member.
Another important feature of the invention concerns the stencil printing machine wherein said micro-convexities and said micro-concavities of the outer circumferential periphery of said rotary press member has a depth of a value above 0.044 mm.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, when the rotary press member presses the printing drum via print medium, there is an adequately big difference in level in the convexities and the concavities such that the concavities have little or no contact with non-fixed ink of print medium, thereby further minimizing transfer of non-fixed ink to the rotary press member.
Another important feature of the invention concerns the stencil printing machine wherein a distance between apexes of said micro-convexities and said micro-concavities of the outer circumferential periphery of said rotary press member has a value below 0.64 mm.
With such a stencil printing machine, the effects of the invention is obtained and, in addition, when the rotary press member presses the printing drum via print medium, there is a narrow distance between the convexities and the concavities formed over the outer circumferential periphery of the rotary press member, interrupting the print image from appearing a visible convexity and concavity pattern.
Another important feature of the invention concerns the stencil printing machine wherein said micro-convexities and said micro-concavities of the outer circumferential periphery of said rotary press member are composed of point-like convexities and concavities.
With such a stencil printing machine, the effects of the invention are obtained and, in addition, the convexities and the concavities can be uniformly formed in either direction over the outer circumferential periphery of the rotary press member.
Another important feature of the invention concerns the stencil printing machine wherein said micro-convexities and said micro-concavities of the outer circumferential periphery of said rotary press member are composed of line-shaped convexities and concavities which are orientated in the same direction as that which print medium is transferred.
With such a stencil printing machine, the effects of the invention are obtained and, in addition, the convexities and the concavities can be regularly and distinctly formed over the outer circumferential periphery of the rotary press member in a direction perpendicular an axial direction thereof.
Another important feature of the invention concerns the stencil printing machine, which further comprises a liquid application unit for applying liquid to the outer circumferential periphery of said rotary press member.
With such a stencil printing machine, the effect of the invention is obtained and, in addition, during separating movement between the rotary press member and print medium, a non-fixed ink area is not split whereas a liquid area is split, thereby preventing non-fixed ink from being adhered to the rotary press member.